Radio controlled remote brake systems for a railway train having a caboose equipped with a motor driven pressure regulating valve are known in the art. An example of one such system is disclosed in U.S. Pat. No. 4,056,286 to Burkett which is assigned to the assignee of the present application. In that system, when a brake application is made at the locomotive by operating the engineer's brake valve device, a radio signal corresponding to the brake valve position is transmitted to the caboose where it is compared with a feedback signal corresponding to the instantaneous position in which the caboose regulating valve is set by its drive motor. The comparison is done digitally in a digital servo mechanism to control a stepping motor that operates the valve.
End of Train (EOT) signaling and monitoring equipment is now widely used, in place of cabooses, to meet operating and safety requirements of railroads. The information monitored by the EOT unit typically includes the air pressure of the brake line, battery condition, warning light operation, and train movement. This information is transmitted to the crew in the locomotive by a battery powered telemetry transmitter.
The original EOT telemetry systems were one-way systems; that is, data was periodically transmitted from the EOT unit to the Locomotive Control Unit or LCU (sometimes called the Head of Train [HOT] unit) in the locomotive where the information was displayed. More recently, two-way systems have been introduced wherein transmissions are made by the LCU to the EOT unit. In one specific application, the EOT unit controls an emergency air valve in the brake line which can be controlled by a transmission from the LCU. In a one-way system, emergency application of the brakes starts at the locomotive and progresses along the brake pipe to the end of the train. This process can take significant time in a long train, and if there is a restriction in the brake pipe, the brakes beyond the restriction may not be actuated. With a two-way system, emergency braking can be initiated at the end of the train independently of the initiation of emergency braking at the head of the train, and the process or brake application can be considerably shortened, with assurance of applying brakes behind any such obstruction.
As will be appreciated by those skilled in the art, in order for a LCU to communicate emergency commands to an associated EOT unit, it is desirable for the LCU to be "armed"; that is, linked to a specific EOT unit by authorized railroad personnel. This is desirable to prevent one LCU from erroneously or maliciously actuating the emergency brakes in another train. To this end the LCU includes a nonvolatile memory in which a unique code identifying an EOT unit can be stored. The LCU also has a row of thumb wheel switches which allows manual entry of codes. Additional background on EOT systems may be had by reference to U.S. Pat. Nos. 5,374,015 and 5,377,938, both of Bezos et al. and assigned to the assignee of this application. The disclosures of these two references are incorporated herewith by reference.
For more effective operation of EOT systems, computer control strategy is needed that automatically establishes operating pressures at the LCU and EOT unit, generate brake commands at the LCU and the EOT units, respond to brake commands generated and transmitted by the LCU, and monitor and analyze a pressure gradient between the locomotive and rear of the train, among other things. It is desirable to perform these functions in an automated way so as to minimize the tasks of railroad personnel, especially the engineer, and at the same time provide the engineer with valuable information on the performance of the train's brake system.